Acetylene generation from hydrocarbons



July 24, 1951 S. P. ROBINSON Filed Aug. 21, 1947 50/ f? Rob/71500 INVENTOR.

Patented July 24, 1951' UNITED STATES PATENT OFFICE ACETYLENE GENERATION mom maooannons Sam I. Robinson, Bartlcsvllle, th., assignor to Phillips Petroleum Company, a corporation of Delaware Application August 21, 1947, Serial 789,795

This invention relates to the production of hydrocarbons high in carbon content, i. e., in

weight percent of carbon, from hydrocarbons low in carbon content by partial combustion with elemental oxygen or oxygen-rich streams, and more particularly to the production of acetylene from paraffin and olefin hydrocarbons, and to apparatus for producing high yields thereof.

8 Claims. (Cl. 260-679) the higher carbon hydrocarbons, for example,

acetylene, have been efi'ective for concentrations from 3% up to, in some cases 10% by volume,'but higher percentages have not been attained and impurities have been formed which are difllcult of removal. c

Among the objects of the present invention are the-continuous production of high-carbon hydrocarbons in high concentration, for example, in excess of of the volume of the initial hydroearbon; more efficient operation of the required apparatus; independent heating means for the hydrocarbon and the oxygen, and a cooperative relationship between the various zones of the hydrocarbon reaction chamber or chambers and the oxygen'heating apparatus. Further advantages of the invention are successively more rapid reaction times as the reaction progresses, successive introduction of oxygen at higher temperatures, decreased partial pressures of the reaction hydrocarbon at successive stages in the reaction, and automatic introduction of oxygen at progressively higher temperatures t intermediate progressive stages of the reaction cycle.

While the invention is particularly adapted to the production of acetylene from paramn hydrocarbons such as ethane, it is to be understood that other hydrocarbons may be used as the starting materials or as intermediates, including olefins such as ethylene. It is also to be understood that the invention is applicable to the Production of olefins from paraflins; for example, ethylene, from ethane; although the most advantageous use of the invention at present, for economic reasons, is in the manufacture of acetylene on a commercial basis at extremely low cost.

In practicing the invention, ethane is first preheated by suitable means and introduced, to-

gether with free oxygen which has also been preheated, into a reaction chamber containing small pebbles of aluminum oxide which efiect thorough dispersion and mixture of the ethane and the oxygen, Each of the reaction chambers contains a fixed bed of refractory pebbles. It is preferred that the ethane be'heated to between 1000 and 1500 F. prior to introduction into the first reaction chamber, and that the oxygen be preheated to a temperature within the range of to- 1000 F. The ellluent from the first reaction chamber, which comprisesrelatively high concentration' of ethylene is then mixed with additional oxygen j which has been preheated to a higher temperature than the initial oxygen, for example from 1000 to 1500 F. The mixture containing the additional increment of preheated oxygen isthen introduced into a second reaction chamber and partial combustion takes place at a higher temperature, for example 2000 to 2500 Rand fora shorter period of time than the initial reaction. The reaction in the first chamber may occur in 0.5'second at a temperature between 1500 and 2000 whereas the reaction in the second chamber may occur in a period of time which is about one-fifth that of the first, e. g., 0.10 second. The reaction may be caused to progress in one or more subsequent reaction chambers by the introduction of additional oxygen heatedto an even higher temperature, for example, 2,000? F. to 2,500 F. This additional increment of oxygen may be mixed with the eliluent'in'a mixing bustle and the admixture introduced into an even smaller reaction chamber having a temperature in excess of 2,500 E, this reaction taking place in a considerably reduced period of time, of the order of 0.02 second. Furtherreaction stages may be carried out, if desired, but it has been found that the concentration of acetylene thus produced from ethane in the el'lluent of the third reaction chamber is in excess of 20% by volume.

The final eflluent containing the acetylene in high concentration is then cooled, for example, by a quenching spray of water or other quenching medium, to a temperature at which the acetylene may be. recovered without further reaction, and the impurities are removed in conventional manner.

While any desired heating means may be used for progressively raising the temperature with the increments of oxygen, it has been found highly desirable and economical to provide a heating chamber. or preferably a series of heating chambers through which the oxygen is passed in the aseaeoe direction of the source of heat. The source of heat is preferably a continuously travelling quantity of heating elements which pass through the oxygen heater or series of heaters countercurrently to the flow of oxygen therethrough. It has been found convenient to use refractory pebbles as the heating elements and to pass them downwardly through a vertically arranged series of heating chambers while passing the oxygen upwardly through the chambers, thereby providing the highest temperatures for the oxygen in the uppermost heating temperature and the lowest temperatures at the bottom of the stack, the intermediate volumes of oxygen being progressively hotter as the oxygen is forced upward. When this arrangement is used for the heater, it is particularly convenient to similarly stack the reaction chambers with the first and largest volume chamber at the lowermost position and the last and smallest chamber at the uppermost position. In accordance with this invention it is preferred to arrange the oxygen heating chambers opposite the respective reaction chambers to which the oxygen at the various temperatures is to be introduced, thereby avoiding heat losses and excessive lengths of the conduits leading from the heaters to the reaction chambers.

Referring to the drawing, which is a diagrammatic representation, the hydrocarbon is preheated by introducing gaseous or liquid fuel and air through the conduit I into a mixing chamber 2 and thence through conduit 3 into a preheater 4. Hydrocarbon is introduced at 5 through a coil 6 within the preheater and thence through conduit 1 to a hydrocarbon distributor 8. While a specific method and apparatus are described for the preheating of the hydrocarbon, it is of course understood that any other suitable means may be used. The preheated hydrocarbon is then fed or forced into a mixing bustle 9 together with preheated oxygen from conduit l into the first reaction chamber ll wherein thermal pyrolysis causes partial dehydrogenation of the hydrocarbon, such as ethane, thereby effecting a high yield of ethylene. The eiiiuent gases from chamber H at elevated temperature are mixed in a second mixing bustle l2 with oxygen introduced at the conduit 13 at higher temperature than the oxygen from conduit Ill. The mixture is then forced into a smaller reaction chamber H heated to a higher temperature than chamber I I, wherein the reaction takes place in a shorter time and the eilluent is mixed in a third mixing bustle IS with still hotter oxygen introduced from conduit 16. The mixture from the bustle l then passes into a still smaller reaction chamber l'l, wherein further partial combustion takes place at a higher temperature than either of the two preceding reactions. The eflluent from the reaction chamber I! has a high acetylene content, 1. e., over 20% by volume, and is withdrawn through conduit l8, and quenched by a fluid from conduit I9 such as a direct spray of water or other quenching medium, whence it emerges at 20.

As the gases pass from the first to the last reaction chamber, the partial combustion takes place at increasingly higher temperatures in the presence of increasing amounts of hydrogen, steam and carbon oxides which effectively depress the partial pressure of the hydrocarbon reactant to insure higher yields of acetylene. The higher yields are also assisted by the decreasing size oi the successive reaction chambers, as well as by the decreasing periods of time for the successive reactions. It is of course desirable to insulate the elements of the entire system including the conduits.

At the same time that the reaction is progressing, oxygen introduced at conduit 2| is forced through a series of heating chambers 22 and 23 at successively higher temperatures. The heating is effected by first introducing refractory pebbles through the conduit or chute 24 into a pebble heating chamber 25 which may be heated by introducing fiuid fuel and air through conduit 26. After the pebbles are heated they descend from the heating chamber 25 through a conduit 21 into chamber'23, where they are partially cooled by the influx of oxygen therethrough which enters through line I3, and thence through conduit 28 into chamber 22 to heat the initial oxygen. to a relatively lower temperature. The pebbles are removed through conduit 29 from the bottom of chamber 22 and are mechanically reintroduced along the path 30 back up to the chute 24 and into the heating chamber 25 to recommence another heating cycle. The stack gases from combustion of the fuel in chamber 25 are vented at conduit 3|. The lower-temperature oxygen is withdrawn from chamber 22 through conduit 32 and is branched into conduits l8 and IS. A portion of the preheated oxygen from conduit 32 is mixed with higher-temperature oxygen from conduit 33, thus yielding an oxygen feed at I! of intermediate temperature. The hottest oxygen, from conduit 33, is in part introduced into the mixing bustle l5 through conduit ii.

The conduits leading from the oxygen heatin chambers to the mixers for the reaction chambers are preferably arranged in straight lines in order to reduce heat losses which would be'occasioned by circuitous paths.

While a vertical arrangement is shown in the drawing for the heating chambers and the reaction chambers, and a gravity flow system for the heating elements is shown for the heating pebbles, it is to be understood that other arrangements may be emplyoed without sacrificing the advantages of the invention.

As a specific example of practicing the invention, three parts by volume of ethane are preheated to 1,200 F. and then mixed in a bustle 9 with one part of oxygen heated to 800 F. from heater 22. The resulting mixture is then passed through a fixed pebble bed in the reaction chamber ll'maintained at 1,650 F. by partial combustion of part of the ethane and cracked products. The eflluent contains in excess of 30% by volume of ethylene and is then further cracked successiiiely in the reaction chambers 14 and I! at increasing temperatures, in reduced reaction times and in the presence of increasing partial pressures of hydrogen, steam, and carbon monoxide by incremental additions of increasingly hot oxygen from the conduits l3 and IE. Reaction times in the successive chambers are 0.5 second, 0.1 second, and 0.02 second, and the respective temperatures at which the pebbles in each of the reaction chambers are maintained are 1,5002,000 F., 2,000-2,500 F.,

and about 2,600 F. The respective temperatures for the oxygen introduced through conduits ll, l3, and I6 are approximately 800 F., 1,250 E, and 2,000 F. The acetylene emerging from the conduit 18 at the top of the stack of reaction chambers is in volumetric concentration in excess of 20%. The eiliuent including acetylene, steam, and carbon oxides is then quenched down to a safe temperature and the impurities are removed in conventional manner.

In view of the many changes and modification that may be madewithout departing from the principlLs underlying the invention, reference should be made to the appended claims for an understanding of the scope of the protection aiforded the invention.

What is claimed is:

1. The process of producing acetylene which comprises, separately preheating reactant hydrocarbon low in carbon content and oxygen, the total amount of oxygen being stoichiometrically insufficient for complete combustion of the reactant hydrocarbon, the oxygen being heated to a temperature below that of the reactant hydrocarbon, mixing the reactant hydrocarbon and oxygen in a first mixing zone of restricted cross section, passing the mixture through a first reaction zone having a cross-sectional area and volume substantially greater than said first mixing zone, admixing the gaseous efiiuent from said first reaction zone in a second mixing zone of restricted cross section with additional oxygen preheated to a temperature higher than that of said first-mentioned oxygen, but lower than the temperature of the reactant gases, passing the resulting mixture through a second reaction zone having a cross-sectional area and volume less than said first reaction zone but greater than said second mixing zone, admixing the gaseous effluent from said second reaction zone in a third mixing zone of restricted cross section with additional oxygen preheated to a temperature higher than that of said second-mentioned oxygen, but lower than the temperature of the reactant gases, passing the resulting mixture through a 1 third reaction zone having a cross-sectional area and volume less than said second reaction zone but greater than any of said mixing zones, quenching the resulting eiliuent from said third reaction zone and recovering acetylene as a prod uct of the process.

2. The process in accordance with claim 1 in which the reactant hydrocarbon is ethane.

3. The process in accordance with claim 1 in which the reactant hydrocarbon is ethylene.

4. The process of producing acetylene which comprises separately preheating reactant hydrocarbon and oxygen, the total amount of oxygen being stoichiometrically insufficient for complete combustion of the reactant hydrocarbon, the oxygen being preheated to 700 to 1000 F., mixing the reactant hydrocarbon and oxygen in a first mixing zone of restricted cross section and passing the mixture through a first reaction zone having a cross-sectional ,area and volume substantially greater than the first mixing zone where the first partial combustion is carried out at about 1000 to 1500 F., admixing the gaseous efiluent from said first reaction zone in a second mixing zone of restricted cross-section with additional oxygen preheated to about 1000 to 1500 F., passing the resulting mixture through a second reaction zone having a cross-sectional area and volume less than said first reaction zone but greater than said second mixing zone, wherein the partial combustion is carried at about 2000 to 2500 F. admixing the gaseous eifluent from said second reaction zone in a third mixing zone of restricted cross-sectional area with additional oxygen preheated to a temperature of about 2000 to 2500 F. and passing the resulting mixture through a third reaction zone having a cross-sectional area and volume less than said second reaction zone, but greater than any of said mixing zones and accomplishing the partial combustion in excess progressively smaller reaction zones at progres sively higher temperatures, comprising, separately preheating the reactant hydrocarbon gas and an amount of oxygen stoichiometrically insufficient for complete combustion, the oxygen being preheated to a lower temperature than the reactant hydrocarbon, passing said oxygen and reactant hydrocarbon into a reaction zone and accomplishing partial combustion of said reactant hydrocarbon in said reaction zone, thereby inducing some temperaturerise therein and repeating said preheating of oxygen and partial combustion of said reactant gases at successive substantial increments of temperature, and finally quenching said reactant gases to recover acetylene therefrom.

8. The process of producing acetylene which comprises separately preheating reactant hydrocarbon having two carbon atoms and oxygen, the total amount of oxygen being stoichiometrically insufiicient for complete combustion of the reactant hydrocarbon, the oxygen being preheated to 700 to 1000 F., mixing the reactant hydrocarbon and oxygen in a first mixing zone of restricted cross section and passing the mixture through a first reaction zone having a cross-sectional area and volume substantially greater than the first mixing zone where the first partial combustion is carried out at about 1000 to 1500 F., admixing the gaseous eflluent from said first reaction zone in a second mixing zone of restricted cross section with additional oxygen preheated to about 1000 to 1500 F., passing the resulting mixture through a second reaction zone having a cross-sectional area and volume less than said first reaction zone but greater than said second mixing zone, wherein the partial combustion is carried at about 2000 to 2500 F. admixing the gaseous efiluent from said second reaction zone in a third mixing zone of restricted cross-sectional area with additional oxygen preheated to a temperature of about 2000 to 2500 F. and passing the resulting mixture through a third reaction zone having a cross sectional area and volume less than said second reaction zone, but greater than any of said mixing zones and accomplishing the partial combustion in excess of about 2500 F. and quenching the resulting eflluent from said third reaction zone and recovering acetylene as a product of the process.

SAM P. ROBINSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,808,168 Hopkins June 2, 1931 2,236,555 Wulff Apr. 1. 1941 2,371,147 Burk Mar. 13, 1945 2,377,245 Krejci May 29, 1945 2,405,395 Bahlke et al Aug. 6, 1946 2.422.501 Rotheli June 17, 1947 

1. THE PROCESS OF PRODUCING ACETYLENE WHICH COMPRISES, SEPARATELY PREHEATING REACTANT HYDROCARBON LOW IN CARBON CONTENT AND OXYGEN, THE TOTAL AMOUNT OF OXYGEN BEING STOICHIOMETRICALLY INSUFFICIENT FOR COMPLETE COMBUSTION OF THE REACTANT HYDROCARBON, THE OXYGEN BEING HEATED TO A TEMPERATURE BELOW THAT OF THE REACTANT HYDROCARBON, MIXING THE REACTANT HYDROCARBON AND OXYGEN IN A FIRST MIXING ZONE OF RESTRICTED CROSS SECTION, PASSING THE MIXTURE THROUGH A FIRST REACTION ZONE HAVING A CROSS-SECTIONAL AREA AND VOLUME SUBSTANTIALLY GREATER THAN SAID FIRST MIXING ZONE, ADMIXING THE GASEOUS EFFLUENT FROM SAID FIRST REACTION ZONE IN A SECOND MIXING ZONE OF RESTRICTED CROSS SECTION WITH ADDITIONAL OXYGEN PREHEATED TO A TEMPERATURE HIGHER THAN THAT OF SAID FRIST-MENTIONED OXYGEN, BUT LOWER THAN THE TEMPERATURE OF THE REACTANT GASES, PASSING THE RESULTING MIXTURE THROUGH A SECOND REACTION ZONE HAVING A CROSS-SECTIONAL AREA AND VOLUME LESS THAN SAID FIRST REACTION ZONE BUT GREATER THAN SAID SECOND MIXING ZONE, ADMIXING THE GASEOUS EFFLUENT FROM SAID SECOND REACTION ZONE IN A THIRD MIXING ZONE OF RESTRICTED CROSS SECTION WITH ADDITIONAL OXYGEN PREHEATED TO A TEMPERATURE HIGHER THAN THAT OF SAID SECOND-MENTIONED OXYGEN, BUT LOWER THAN THE TEMPERATURE OF THE REACTANT GASES, PASSING THE RESULTING MIXTUR THROUGH A THIRD REACTION ZONE HAVING A CROSS-SECTIONAL AREA AND VOLUME LESS THAN SAID SECOND REACTION ZONE BUT GREATER THAN ANY OF SAID MIXING ZONES, QUENCHING THE RESULTING EFFLUENT FROM SAID THIRD REACTION ZONE AND RECOVERING ACETYLENE AS A PRODUCT OF THE PROCESS. 